The oil polluting Louisiana’s marshes lies about 5,000 miles away from Britain’s coastline. But while wildlife, the fishing industry and tourism here are safe from the slick, the leak is hitting Britons’ pockets and their pride. By Wednesday night, BP's shares had lost more than half of their market value -- or at least $71 billion -- in the 52 days since the crisis began. Almost every pension fund in the U.K. owns shares in the energy giant, raising serious questions about the impact the firm's plummeting value will have on the retirement plans for millions of Britons. President Barack...